JPH03170071A - Current detector - Google Patents

Abstract

PURPOSE:To obtain the current detector which has a small hysteresis voltage corresponding to the optional purpose of use and detection current range by inserting another ferromagnetic material into the gap part of a ferromagnetic material core. CONSTITUTION:The current detector is constituted by forming a toroidal core 3 of directional silicon steel so as to widen the detection current range, forming the gap where a magnetism sensing element is inserted in the silicon steel core 3, and laminating and inserting a 'Permalloy(R)' thin plate which has the same sectional area with the silicon steel core into the expanded gap. In this case, the residual magnetism of the whole core is reduced and the hysteresis voltage falls. The 'Permalloy(R)' 4 suppress a decrease in the sensitivity of the current detector. Then magnetic flux density is smaller nearby the gap 1 of the ferromagnetic material core than in the entire core and the detection current range which is closer and closer to the directional silicon steel is obtained as the 'Permalloy(R)' of the gap part is thinner and thinner.

Description

[Detailed Description of the Invention] Industrial Field of Application] The present invention relates to a current detector used in electronic equipment or electric machines, etc., and in particular, the present invention relates to a current detector used in electronic equipment or electric machines, etc. , relates to the configuration of a ferromagnetic core of a current detector of the type in which a magnetic sensing element is configured within the gap.

[Prior Art] Conventionally, in this type of current detector (Fig. 2). The ferromagnetic core 3 used in the part that forms the magnetic circuit has... In particular, ferromagnetic material A with a high saturation magnetic flux density is used to widen the detection current range, or ferromagnetic material B with a low coercive force is used to reduce detection errors. A magnetic gap 1 is formed into which the element 2 is inserted, and a magnetic sensing element 2 is inserted into the magnetic gap 1.
An output voltage proportional to the magnitude of the current is obtained by the magnetic sensing element 2 inserted into the magnetic gap 1 which generates a magnetic field proportional to the current to be measured flowing through the through wire 5.

The output voltage proportional to the current of the through wire 5 detected by the magnetic sensing element 2 is . The magnitude of the through current is detected by amplifying it with a signal amplification circuit to obtain an output voltage proportional to the magnitude of the current.

[Problem to be solved by the invention] However, in conventional current detectors, the residual magnetism generated in the gap is amplified as is due to the hysteresis characteristics of the ferromagnetic core used in the part forming the magnetic circuit. Output as detection error (hysteresis voltage). Furthermore, the saturation magnetic flux density of the ferromagnetic core directly affects the detection current range. The ferromagnetic material that makes up this ferromagnetic core is a major factor in determining the performance of the current detector, but the ferromagnetic material A, which has a high saturation magnetic flux density, has the disadvantage of having a large coercive force.

Therefore, a current detector using ferromagnetic material A has a characteristic that the detection current range is wide, but the hysteresis voltage is also large, as shown in FIG. 4 (2). In addition, ferromagnetic material B with a small coercive force has a low hysteresis voltage, but its saturation magnetic flux density is low, as shown in Figure 4 (■), so the detection current range is small. It could not be used for large current detectors. By selecting this ferromagnetic material, the detection current is limited to a current detector with a large detection current range and a large detection error (Fig. 4 ■) or a current detector with a small detection error and a small detection current range (Fig. 4 ■). It was difficult to design a current detector with a small hysteresis voltage depending on the range.

[Means for Solving the Problems] According to the present invention, in order to eliminate such drawbacks of the conventional technology. In the ferromagnetic core of a current detector, a gap is provided in a part of the magnetic path of the toroidal ferromagnetic core, and a magnetically sensitive cord is inserted into the gap. By inserting another ferromagnetic material into the gap of the ferromagnetic core, the saturation magnetic flux density,
A current detector is obtained in which the core is constructed by connecting two types of ferromagnetic materials with different coercive forces in series.

[Structure of the Invention] In a ferromagnetic core of a current detector, a gap is provided in a part of the magnetic path of the toroidal ferromagnetic core, and a magnetic sensing element is inserted into the gap. As shown in Fig. 3, the gap portion of the toroidal ferromagnetic core 3 made of a ferromagnetic material A with high saturation magnetic flux density and large coercive force is enlarged, and the volume of the ferromagnetic material A is reduced. While the hysteresis voltage is reduced by reducing the residual magnetism of the core, the sensitivity of the current detector decreases due to the enlargement of the magnetic gap 1. This is because ferromagnetism has a small coercive force and a low saturation magnetic flux density due to the enlarged gap. Hold it down by inserting material B. As described above, by combining two types of ferromagnetic materials with different magnetic flux densities and coercive forces to construct a ferromagnetic core as shown in Figure 1, the hysteresis voltage and detection current range of the current detector can be adjusted. It is characterized by being able to be designed arbitrarily.

[Function] In the core of the current detector configured as shown in Fig. 1, the residual magnetism decreases due to the decrease in the proportion of ferromagnetic material A with a large coercive force to the entire ferromagnetic core, and only ferromagnetic material A decreases. The hysteresis voltage is lower than that of a current detector whose core is made up of . or. By pushing ferromagnetic material B with a small coercive force into the enlarged magnetic gap 1. This suppresses the decrease in sensitivity as a current detector. The detection current range is determined by the saturation point of ferromagnetic material B, which has a small saturation magnetic flux density in the gap 1 portion, but the magnetic flux density near the magnetic gap 1 is distributed to be smaller as it gets closer to the gap. Even if the average magnetic flux density of the ferromagnetic core exceeds the saturation magnetic flux density of ferromagnetic material B, it is inserted thinly into the gap 1 portion. Ferromagnetic material B does not saturate. The larger the proportion of ferromagnetic material B, the smaller the hysteresis voltage. The thinner the ferromagnetic material B in the gap, the wider the detection current range. Therefore, by using a ferromagnetic core configured as shown in Fig. 1 in a current detector, the ferromagnetic core can be adjusted depending on the ratio of ferromagnetic materials A and B, depending on the saturation magnetic flux density and coercive force of the two ferromagnetic materials. Any current detector can be designed with characteristics intermediate between those using only magnetic material A or ferromagnetic material B.

Example C] Example will be explained with reference to the drawings. FIG. 2 is a front view of the configuration of a conventional current detector. A toroidal ferromagnetic core 3 is passed through a through wire 5 through which a current to be measured flows, and the ferromagnetic core 3 focuses the magnetic flux generated by the current in the through wire 5, and the magnetic gap 1 of the ferromagnetic core 3 is A magnetic flux is generated in the space of the magnetic gap 1, and the intensity of the magnetic flux is measured by the magnetic sensing element 2. 4 shows the detection current range and hysteresis voltage when using only grain-oriented silicon steel and vermalloy for the ferromagnetic core 3 of the current detector shown in FIG. 2.

FIG. 3 shows the tfl of a ferromagnetic core embodiment of the current detector of the present invention. Grain-oriented silicon steel is a ferromagnetic material with high saturation magnetic flux density and large coercive force. A ferromagnetic core like the example (shown in Figures 3 (a), (b) and (c)) can be purchased by series connection of permalloy, which is a ferromagnetic material with low saturation magnetic flux density and small coercive force. are doing. In order to widen the detection current range, a toroidal core 3 is formed from grain-oriented silicon steel, and in addition to a magnetic gap 1 to provide a magnetic sensing element, a permalloy 4 is added to the silicon steel core 3. A gap is formed for this purpose, and permalloy thin plates having the same cross-sectional area as the silicon steel core are laminated to form an expanded gap 1. Grain-oriented silicon steel, which has a large coercive force, is reduced by the volume of the inserted permalloy, and since the coercive force of vermalloy is less than 1/10 of that of grain-oriented silicon steel, the residual magnetism of the entire core decreases, and the hysteresis voltage decreases. Decrease. Permalloy 4 suppresses the decrease in sensitivity of the current detector due to expansion of the gap. The detection current range is determined by the saturation point of Permalloy 4, which has a small saturation magnetic flux density. The magnetic flux density near the gap 1 of the ferromagnetic core is lower than that of the entire core, and the thinner the permalloy 4 in the gap, the closer the detection current range to grain-oriented silicon steel can be obtained. The detected current range and hysteresis voltage when the current detector shown in FIG. 3 (a) of this embodiment is used in the ferromagnetic core of the current detector shown in FIG. 2 are shown in FIG.

[Effects of the Invention] As is clear from the above invention, according to the present invention, in the toroidal ferromagnetic core of the current detector, the gap formed by the ferromagnetic material A with high saturation magnetic flux density is large. By inserting ferromagnetic material B with a low coercive force into the ferromagnetic core, this can be achieved especially in large current detectors where a ferromagnetic core made of ferromagnetic material B with a low saturation magnetic flux density cannot be used. It is now possible to provide a current detector with a small hysteresis voltage that is suitable for any application and detection current range.

[Brief explanation of the drawing]

Fig. 1 is a ferromagnetic core portion of a current detector according to an embodiment of the present invention, Fig. 2 is a front view of the configuration of a generally used current detector, and Fig. 3 is a current detector according to the present invention. FIG. 4 (A) is a diagram showing an embodiment of the detector, and FIG. (b) is a diagram showing the relationship between the detection current range and hysteresis voltage of the current detectors of the conventional and one embodiment of the present invention. ■Current detector using grain-oriented silicon steel core. ■Current detector using an embodiment of the present invention (oriented silicon steel + vermalloy) core. ■Current detector using permalloy core. 1...Magnetic gap. 2...Magnetic sensing element, 3...Ferromagnetic {O material A (oriented silicon 11i4), 4...Ferromagnetic material B (permalloy), 5...Through electric wire, 6...Circuit component , 7... Circuit length support plate, 8... External terminal. Figure 3 (a) Input current (mouth) (mouth) Input current

Claims (1)

[Claims] (1) In a ferromagnetic core of a current detector in which a gap is provided in a part of the magnetic path of the toroidal ferromagnetic core and a magnetic sensing element is inserted into the gap, the gap portion of the ferromagnetic core is A current detector characterized in that a core is constructed by a series connection of two types of ferromagnetic materials having different saturation magnetic flux densities and coercive forces by inserting other ferromagnetic materials.